Feuchteklasse

Feuchteklasse, or moisture class, is a classification used in the German-speaking construction and wood-processing sectors to describe the expected moisture exposure of materials, particularly wood and wood-based products. The purpose of the classification is to guide the handling, processing, installation, and long-term performance of materials by aligning their moisture content with the environment in which they are used. By designating a material to a specific Feuchteklasse, manufacturers and builders aim to minimize dimensional changes, inhibit deterioration, and ensure compatibility with finishes, fasteners, and adhesives.

In practice, Feuchteklassen are typically labeled with a sequence such as FK0, FK1, FK2 and FK3 (sometimes written F0–F3 in other standards). Each class corresponds to a defined range of moisture exposure and target moisture content for the material, reflecting different installation or usage environments. FK0 represents the driest conditions intended for very dry interiors, FK1 for normal indoor humidity, FK2 for humid or sheltered outdoor exposure, and FK3 for exterior exposure or direct ground contact. The exact numerical limits and the names of the classes can vary by standard, but the concept remains the same: the class communicates how damp a material may become and how it should be treated or finished.

The Feuchteklasse informs decisions across the product life cycle, including drying processes, storage, transport, gluing, coating, and ventilation considerations. It is especially important for ensuring the performance and durability of timber and wood-based components in building projects. See also moisture content, wood in construction, and related German standards for timber products.